Electrostatic deflection type cathode-ray tube with a plurality of electron guns

ABSTRACT

An electrostatic deflection type cathode-ray tube wherein a mesh electrode is disposed between a phosphor screen and at least two electron guns juxtaposed with their axes inclined with respect to the axis of the tube, and wherein a post-accelerating electrode system for the formation of a divergent electron lens is provided by means of an internal conductive film deposited on the inner wall surface of the funnel portion of the bulb of the tube and the mesh electrode, whereby there is eliminated the inconvenience of any occurrence of geometry distortion of raster due to the inclined disposition of the electron guns with respect to the axis of said tube.

United States Patent 11 1 Kimura 1 51 Jan.2,1973

54 ELECTROSTATIC DEFLECTION TYPE 2,933,640 4/1960 Komptner ..313/70 R 2,179,916 11/1939 Bouwers ..313/s3 CATHODE RAY TUBE WITH A 3,497,763 2/1970 Hasker ..315/31 TV PLURALITY OF ELECTRON GUNS [75] Inventor: Masamichi Kimura, Takatsuki,

Primary Examiner-Benjamin A. Borchelt J n Assistant ExaminerS. C. Buczinski Att0rney--Stevens, Davis, Miller & Mosher [73] Ass1gnee: Mntsushita Electronics Corporation,

Osaka, Japan [57] ABSTRACT [22] Filed: 17v 1970 An electrostatic deflection type cathode-ray tube [21] Appl. No.: 55,678

[30] Foreign Application Priority Data wherein a mesh electrode is disposed between a phosphor screen and at least two electron guns juxtaposed with their axes inclined with respect to the axis of the tube, and wherein a post-accelerating electrode system for the formation of a divergent electron July 23, Japan lens is provided means of an inte n l nd ti film deposited on the inner wall surface of the funnel [52] [1.8. C]. ..3l5/13 C, 313/70 R, 315431 TV portion of the bulb of the tube and the h l [51] lint. Cl. ..H01J 29/50 trode whereby there is eliminated the inconvenience Field of Search 13 31 of any occurrence of geometry distortion of raster due 313/ 70 C to the inclined disposition of the electron guns with respect to the axis of said tube. [56] References Cited UNITED STATES PATENTS 4 Claims, 4 Drawing Figures 3,537,097 10/1970 Gumpertz ..3l3/70 R i? E, i r it PATENTED JAN 2 7 SHEET 2 0F 2 ELECTROSTATIC REFLECTION TYPE CATHGDE- RAY TUBE WITH A PLURALITY F ELECTRON GUNS This invention relates to an electrostatic deflection type cathode-ray tube provided with a plurality of electron guns.

In an electrostatic deflection type cathode-ray tube, it has hitherto been the practice that a first electron gun and a second one are accommodated in the neck portion of a bulb in such a manner that their respective axes are inclined with respect to the axis of the tube, and that electron beams emitted from the two electron guns are accelerated by means of a post-accelerating electrode system formed by conductive films deposited on the inner wall surface of the funnel portion of the bulb, whereby the respective traces are caused to appear on a common phosphor screen face.

In the case of the vertical arrangement of two electron guns, that is, one gun is disposed upper and the other gun is disposed lower, however, the Y (vertical)- axial sensitivity varies in the vertical direction on the phosphor screen face and the Y traces do not become perpendicular on both extreme sides, creating distortion and difficulties in measurement. In the case of the horizontal arrangement of two electron guns, other distortions occur. For this reason, it is generally required to join, with a conductive helical member, the two conductive films which form the post-accelerating electrode system. However, it has been found that when the V /V ratio between the voltages V, and V applied to the two conductive films exceeds six, the prior art cathode-ray tube can no longer be put to prac tical use.

The present invention has as its principal object eliminating such distortion as mentioned above, and in addition, providing the technical advantages of improving the intensity of traces and of facilitating the observation ofhigh-speed phenomena.

The invention will now be described in detail with reference to the accompanying drawings, in which;

FIG. 1 is a side sectional view of a prior art cathoderay tube of the electrostatic deflection type;

FIG. 2 is a front view of the prior art cathode-ray tube;

FIG. 3 is a side sectional view of an electrostatic deflection type cathode-ray tube embodying the invention; and

FIG. 4 is a side sectional view for illustrating the essential portions of the embodiment.

Referring to FIG. 1, a first electron gun l and a second gun 2 juxtaposed thereto at an inclination of a (approximately 3), are accommodated in the neck portion of a bulb 3. On the inner wall surface of the face panel of the bulb 3, a phosphor screen 4 is attached. The inner wall surface of the funnel portion has first and second conductive films 5 and 6 applied thereon. A post-acceleration electrode system formed by the conductive films 5 and 6 exerts an accelerating action upon electron beams 7 and 8 which are respectively emitted from the electron guns l and 2. On the other hand, a convergent electron lens 9 formed by the electrode system imparts a deflecting action on the electron beams to the tube axis. Thus, the electron beams 7 and 8 impinge upon the common phosphor screen 4, and produce their respective traces thereon.

In this case, however, the trace drawn by the first electron gun 1 and that depicted by the second gun 2 appear in regions represented by A and B in FIG. 2, respectively. As apparent from the drawing, Y-axial sensitivity varies in the vertical direction on the face of the phosphor screen 4, and the Y traces become nonperpendicular on both extreme sides. Such distortion will appear more conspicuously, as the VJV, ratio becomes larger between the voltages V, and V applied to the conductive films 5 and 6, respectively, which constitute the post-acceleration electrode system.

According to a typical embodiment of the electrostatic deflection type cathode-ray tube of the invention, as shown in FIG. 3, the mutual inclining angle [3 between the first electron gun I and the second gun 2 juxtaposed thereto is made larger than the aforementioned value (1, and further, a mesh electrode 10 is interposed between the electron guns 1, 2 and the phosphor screen 4'. An angle fi/2; that is, the angle at which the first electron gun I or the second gun 2 is inclined with respect to the axis of the cathode-ray tube may be usually selected from a range of 2.5 to 7.5". A lens-characteristics correcting annulus 11 is obliquely arranged in such a way as to surround the mesh electrode 10, and therewith, an internal conductive film 12 is deposited on the inner wall surface of the funnel portion of the bulb 3 in a manner to correspond to the mesh electrode 10. A metal backing layer 13 is connected with the internal conductive film 12, while a metallic shielding cylinder 14 is connected with the mesh electrode 10 to support it.

With such a construction as described above, the mesh electrode 10 has a voltage V of approximately 800 to 3,000V applied thereto, while the internal conductive film 12 is impressed with a voltage V two to ten times as high as the voltage V i.e., amounting usually to approximately 4,000 to 25,000V. In addition, a voltage V applied to the lens-characteristics correcting annulus 11 is appropriately selected. Then, there may be formed a divergent electron lens as shown by the reference numeral 15 in FIG. 3. The electron lens 15 exerts a diverging action upon the electron beams 7 and 8 flowing respectively from the electron guns I and 2 which are disposed at the angle 5, and thereby the incident angles of the respective electron which strikes upon the phosphor screen 4 are made smaller than those in FIG. 1. Accordingly it is possible to provide, in effect, a measure which is substantially equivalent to disposition of the first and second electron guns 1 and 2 near the tube axis, and hence, the occurrence of the geometry distortion of raster is reduced which is due to the inclined disposition of both the electron guns 1 and 2 with respect to the axis of the tube.

Furthermore, as shown in FIG. 4 an electron beam emitted from one electron gun and subjected to a divergent type deflecting action with the electron lens, is herein refracted at angles of 0 9 and 0 it being possible to establish, through the effect of the lenscharacteristics correcting annulus 11 and, if necessary, through the effect of curvation of the mesh 10, the condition of 6: 0 8 In this case, the geometry distortion of rastor may be reduced which is due to the inclined disposition of the electron guns with respect to the tube axis. The reference numeral 16 designates one of the equipotential lines.

Furthermore, the configuration and arrangement of the conductive film 12 as well as the lens-characteristics correcting annulus 11 may be subject to suitable modifications. In addition, it is permitted to couple the lens-characteristics correcting annulus 11 with the mesh electrode or to form the former integrally with the latter. Also, in addition, the ring 11 may be dispensed with.

As described above, in accordance with the electrostatic deflection type cathode-ray tube of the invention, a mesh electrode is disposed between a phosphor screen and at least two electron guns are juxtaposed with their axes inclined with respect to the tube axis; a divergent electron lens is formed by the mesh electrode, an internal conductive film and, if necessary, a lens-characteristics correcting annulus; and electron beams emitted from the electron guns have their incident angles upon the screen made narrower. Thereby, the invention provides such various effects that the occurrence of the geometry distortion of the raster as referred to above may be eliminated, the V /V ratio may be selected to be over 10, the intensity of trace is improved, and that the observation of highspeed phenomena is made easier.

What is claimed is:

1. An electrostatic deflection type cathode-ray tube wherein a mesh electrode is interposed between a phosphor screen and at least two electron guns juxtaposed with each of their axes inclined at Bl2 with respect to the axis of said cathode-ray tube, and wherein a post-accelerating electrode system for formation of a divergent electron lens is provided by means of an internal conductive film deposited on the inner wall surface of the funnel portion of the bulb of said cathode-ray tube and said mesh electrode.

2. An electrostatic deflection type cathode-ray tube according to claim 1, wherein the inclination B/2 is selected from a range of 2.5 to 7.5.

3. An electrostatic deflection type cathode-ray tube according to claim 1, wherein said post-accelerating electrode system comprises an annular electrode for correcting the characteristics of said electron lens, which electrode is arranged to surround said mesh electrode.

4. An electrostatic deflection type cathode-ray tube according to claim 1, wherein the axes of said at least two electron guns intersect to each other before said phosphor screen. 

1. An electrostatic deflection type cathode-ray tube wherein a mesh electrode is interposed between a phosphor screen and at least two electron guns juxtaposed with each of their axes inclined at Beta */2 with respect to the axis of said cathoderay tube, and wherein a post-accelerating electrode system for formation of a divergent electron lens is provided by means of an internal conductive film deposited on the inner wall surface of the funnel portion of the bulb of said cathode-ray tube and said mesh electrode.
 2. An electrostatic deflection type cathode-ray tube according to claim 1, wherein the inclination Beta */2 is selected from a range of 2.5* to 7.5* .
 3. An electrostatic deflection type cathode-ray tube according to claim 1, wherein said post-accelerating electrode system comprises an annular electrode for correcting the characteristics of said electron lens, which electrode is arranged to surround said mesh electrode.
 4. An electrostatic deflection type cathode-ray tube according to claim 1, wherein the axes of said at least two electron guns intersect to each other before said phosphor screen. 